Characterization of gametophytic self-incompatibility of superior clones of Coffea canephora

The ability to avoid self-pollination is a trait that evolved as a manner of reducing the deleterious effects of inbreeding in various allogamous plant species, including Coffea canephora. The aim of this study was to perform directed hybridizations to characterize the compatibility groups of superior C. canephora clones, since plant selection can reduce variability for this trait. For that purpose, directed hybridizations were carried out in cross arrangements using a balanced diallel without self-fertilization and without reciprocals. The genotypes evaluated were derived from open pollination and from directed hybridizations using Encapa03 as a male parent donor of pollen grains and Robusta640, Robusta 2258, and Robusta1675 as female parent receptors of pollen grains. To control the occurrence of type I and type II errors, the likelihood ratio test was used. Compatible crosses were predominant (73.7%). Compatible crosses exhibited a mean rate of fruit set of 44%, with amplitude from 26% to 77%. Of the total of 80 crosses performed, three crosses exhibited unexpected results according to the grouping proposed (P08 x P16, P09 x P15, P09 x P16). From the degree of kinship, the genealogy of the S gene and the segregation of the alleles from one generation to another was estimated. The genotypes P12, P14, and P10 exhibited the highest estimates of LOD score associated with their clustering in groups I, II, and III. These genotypes may be used as tester plants of their compatibility groups.